Heat exchanger insulation gap

ABSTRACT

An aircraft heat exchanger that exchanges heat between fluid, like air, to be warmed and a medium, like a liquid, to be cooled has a first path that encounters the fluid to be warmed and carries the medium at a first temperature. A second path carries the medium at a second temperature adjacent to the first path. An insulation gap is disposed between the first path and the second path so that heat exchange between the first and second path is minimized.

BACKGROUND

Plate fin heat exchangers generally consist of a core formed of a plurality of stacked layers. Each layer has a plurality of continuously corrugated or finned elements that are arranged to form a plurality of channels. The channels in one layer may lie in transverse or parallel relation to the channels formed in adjacent layers. A parting sheet separates the adjacent layers. Fluids having differing amounts of heat energy flow through the channels of adjacent layers so that heat energy may be transferred from fluid to fluid.

Environmental control systems (“ECS”) that utilize air cycle machines are well known. ECS systems generally control the temperature and humidity of air within an enclosed environment, such as an aircraft cabin, and usually include a compressor for pressurizing air input thereto, and a turbine for expanding and cooling the air. Some turbines are capable of delivering air at temperatures as low as 100° F. below zero.

At such cold temperatures moisture within the air may be precipitated out in the form of snow or ice. The ice and snow may clog and shut down any downstream components such as heat exchangers. If a heat exchanger becomes clogged, heat transfer among the fluids flowing therethrough may be severely reduced. The air from the turbine may not warm to usable levels for cabins and the fluid that warms the air from the ECS may not be cooled enough for effective downstream use.

SUMMARY

According to a non-limiting embodiment, an aircraft heat exchanger that exchanges heat between fluid, like air, to be warmed and a medium, like a liquid, to be cooled has a first path that encounters the fluid to be warmed and carries the medium at a first temperature. A second path carries the medium a second temperature adjacent to the first path. An insulation gap is disposed between the first path and the second path so that heat exchange between the first and second path is minimized.

According to a further non-limiting embodiment, a method for cooling a medium and warming a fluid in a heat exchanger is proposed. The method includes providing a first path for carrying the medium at a first temperature and encountering the fluid to be warmed, providing a second path for carrying the medium adjacent to the first path at second temperature, and providing an insulation gap between the first path and the second path such that heat exchange between the first and second path is minimized.

According to a still further non-limiting embodiment, a heat exchanger that exchanges heat between fluid, like air, to be warmed and a medium, like a liquid, to be cooled has a first path carrying the medium at a first temperature and encounters the fluid to be warmed. A second path carries the medium adjacent to the first path but the medium in the second path has a second temperature. An insulation gap is disposed between the first path and the second path so that heat exchange between the first and second path is minimized and so that a probability of freezing on the first path of the fluid is minimized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a heat exchanger of the invention.

FIG. 2 is an alternative embodiment of the invention.

DETAILED DESCRIPTION

Referring now to FIGS. 1 and 2, the heat exchanger 10 of the invention is shown. The heat exchanger 10 has a section of melt fins 15, an air gap 20, and main fins 25. A medium (or fluid indicated by arrows 30), which acts in this embodiment as an anti-freeze like a mixture of propylene glycol and water, circulates through the fin sections 15, 25 of the heat exchanger 10 as will be discussed herein. Air 35 passing from an air cycle machine (“ACM”) 40 passes through the heat exchanger 40 to be warmed by the medium 30 in the fin sections 15, 25 of the heat exchanger for use in an aircraft cabin 45. The air passes from the ACM 40 to the cabin 45 through layers (not shown) in the heat exchanger 10 that are to adjacent to the fin sections 15, 25 so that heat may be exchanged between the layers in the fins. The air gap 20 is disposed between the melt fins 15 and the main fins 25 within the heat exchanger 10.

As shown in FIG. 1, the medium 30 flows through the melt fins 15, after entering an inlet melt header 50, passes downwardly to a fin outlet header 55 through piping 60 outside the heat exchanger 10 to an inlet main header 65 to the main fins 25. As shown in both FIGS. 1 and 2, the medium flows in a tortuous path going upwardly through a first section 70 of main fins, turns through a second section 75 of main fins turns through a third section 80 of main fins, passes through a fourth section 85 of main fins and then outwardly through a medium outlet header 90. The air gap 20 is located between the melt fins 15 and the fourth section 85 of the main fins 25. One will understand that the terms upwardly and downwardly used herein are relative to the drawings shown and other directions and orientations are contemplated herein. Similarly, the number of turns and passes the medium takes while flowing through the heat exchanger 10 depends on the heat load to be removed and thus more or less passes are also contemplated herein.

After passing through the medium outlet header 90, the medium 30 cools heating loads of an aircraft including motor controllers for hydraulic pumps and compressors (shown schematically as 95). The medium 30 after cooling those objects (not shown) is delivered back to the inlet melt header 50. The medium 30 is moved through the heat exchanger and the heating loads by a pump or series of pumps that may be placed as required, shown schematically as 100.

Referring to FIG. 2, the medium 30 does not exit the heat exchanger 10 via fin outlet header 55 and reenter the heat exchanger via inlet main header 65 as shown in FIG. 1. The conduit 105 shown in FIG. 2 carries the medium 30 to the first section 70 of the main fins 25 without leaving the heat exchanger 10. Note also that the air gap 20 fully extends along the bottom of the second 75, third 80 and fourth 85 main pass main fins to further minimize heat transfer between the main fins 25 and the medium 30 in the conduit.

As stated above, the main fins 25 and the melt fins 20 are separated by the air gap 20. The air gap 20 which may be unsealed (see 105 as shown in FIG. 1) or sealed as shown in FIG. 2. If the air gap is unsealed, i.e. open to ambient, a user may detect leakage outside the heat exchanger by noticing medium outside of the heat exchanger. By sealing the insulation gap as shown in FIG. 2, the air barrier acts to minimize heat flow between the melt fins and the main fins.

As medium 30 returns from the heating loads 95, it is at its warmest temperature, in this case 70° F. as it enters the melt fins 15. The air 35 from the ACM 40 as it strikes the melt fins 15 is at its lowest temperature in this case −20° F. Because of the warmth of the melt fins 15, the probability that ice and snow will clog the fin sections 15, 25 of the heat exchanger 10 are minimized. The medium drops from 70° F. to about 55° F. after leaving the melt fins 15 and is conducted to the first section 70 of the main fins 25 by either the piping 60 as shown in the embodiment if FIG. 1 or the conduit 105 as shown in FIG. 2 for further cooling. In both embodiments, the air gap 20 keeps the relatively warm medium in and exiting from the melt fins 15 from warming the medium in the successively cooler medium in the fourth section 85 of the main fins 15 as shown in FIG. 1 and the second section 75, third section 80, and the fourth section 85 as shown in FIG. 2.

The medium passes through the main fins 25 in the tortuous path counter to the flow of air 35 through the heat exchanger to lower the temperature of the medium

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. For instance, the air gap 20 may be placed in the heat exchanger in position where it is important to separate relatively warm sections of a medium from cooled sections of the medium. Also, the fluid and medium described herein can substitute for one another and other flow paths may be used. The scope of legal protection given to this disclosure can only be determined by studying the following claims. 

1. A heat exchanger for an aircraft, said heat exchanger exchanging heat between fluid to be warmed and a medium to be cooled said heat exchanger comprising; a first path for said medium having a first temperature, said first path encountering fluid to be warmed, a second path for said medium adjacent to said first path, said medium in said second path having a second temperature, and an insulation gap between said first path and said second path such that heat exchange between said first and second path is minimized.
 2. The heat exchanger of claim 1 wherein said medium is antifreeze.
 3. The heat exchanger of claim 1 wherein said fluid is air.
 4. The heat exchanger of claim 1 wherein said insulation gap is filled with a gas.
 5. The heat exchanger of claim 4 wherein said insulation gap is open to ambient.
 6. The heat exchanger of claim 4 wherein said insulation gap is closed to ambient.
 7. The heat exchanger of claim 1 wherein said first path encounters said fluid when said fluid is at its coldest temperature.
 8. The heat exchanger of claim 7 wherein said second path carries said medium when said medium is at its coldest temperature.
 9. The heat exchanger of claim 7 wherein said first path carries said medium when said medium is at its warmest temperature.
 10. A method for cooling a medium and warming a fluid in a heat exchanger, said method comprising: providing a first path for carrying said medium having a first temperature, said first path encountering said fluid to be warmed, providing a second path for carrying said medium adjacent to said first path, said medium in said second path having a second temperature, and providing an insulation gap between said first path and said second path such that heat exchange between said first and second path is minimized.
 11. The heat exchanger of claim 10 further comprising: providing said fluid at its coldest temperature when said fluid encounter said first path.
 12. The heat exchanger of claim 11 further comprising providing said medium at its warmest temperature in said first path.
 13. The heat exchanger of claim 11 further comprising providing said medium at its coolest temperature in said second path.
 14. A heat exchanger, said heat exchanger exchanging heat between fluid to be warmed and a medium to be cooled said heat exchanger comprising; a first path for said medium having a first temperature, said first path encountering fluid to be warmed, a second path for said medium adjacent to said first path, said medium in said second path having a second temperature, and an insulation gap between said first path and said second path such that heat exchange between said first and second path is minimized so that a probability of freezing on said first path of said fluid is minimized.
 15. The heat exchanger of claim 14 wherein said medium is antifreeze.
 16. The heat exchanger of claim 14 wherein said fluid is air.
 17. The heat exchanger of claim 14 wherein said insulation gap is filled with a gas.
 18. The heat exchanger of claim 17 wherein said insulation gap is open to ambient.
 19. The heat exchanger of claim 17 wherein said insulation gap is closed to ambient. 